Agate, probably the most common and valuable gemstone, is a variety of silica formed by volcanic activity. A multitude of shapes and colors are caused by mineral impurities in the silica. It is these impurities which make the fire agate distinctive. fire agate is considered a gemstone because of the play of the colors beneath its surface that is formed much as a pearl is formed in an oyster. Volcanic water seeps into cracks and crevices below the earth's surface. The impact of the water drops separate some minerals from the water; the mineral stays and the agate grows. Fire agates are said to offer all the fiery color of gem opals, are less costly, are superior in hardness, and will not fade.
Arizona is the only State currently to have commercial production of fire agate. Fire agate is a form of chalcedony which contains inclusion of iron oxides that result in a play of colors much like that of precious opal. Eleven operations in Arizona report either commercial production of fire agate or dig-for-fee production. The material is produced in Graham, Greenlee, Maricopa, Mohave, and Yuma Counties.
Fire agate is cut into freeform and calibrated cabochons for use in the manufacture of silver and gold jewelry. The material is popular in the southwest and with hobbyist lapidaries throughout the United States. Fire agate also has been used and is currently used in Indian style jewelry.